Field
The invention relates to a neutralization plant comprising at least one reaction chamber having a first feed for an acid-containing product and at least one further feed for a base-containing product, wherein at least one of the feeds comprises at least one valve means for controlling the inflow amount into the reaction chamber and at least one ion controller apparatus set up for controlling the valve means. The invention further relates to a method for neutralizing an acid-containing or base-containing product and to an ion controller apparatus.
Description Of Related Art
Chemical plants producing an acid-containing product or a base-containing product as principal products and/or byproducts are found in industry. For example a plant set up for producing 2,4-toluene diisocyanate (TDI) can produce hydrochloric acid as a byproduct. The hydrochloric acid may initially be intermediately stored in suitable storage containers to subsequently be transported further and/or made available to other chemical plants.
Disruptions can have the effect that the storage capacity limits for the hydrochloric acid are reached and no further hydrochloric acid can be stored. In the prior art it is customary to shut down the chemical plant in such a case. Particularly in the case where the produced acid or base is merely a byproduct shutdown of the chemical plant is accompanied by significant economic disadvantages for the operator because the principal product can no longer be produced.
In addition it is generally known from the prior art to neutralize an acid-containing product with a base-containing product (or vice versa) in a neutralization plant. A neutralization plant from the prior art may contain a reaction chamber. The reaction chamber may comprise a first feed, for example for an acid-containing product, and a further feed, for example for a base-containing product. At least one of the feeds may comprise a valve means to control the flow of the corresponding product into the reactor chamber.
For example in the above-described TDI plant the neutralization plant may comprise a first feed for the byproduct of the TDI plant, in the present case hydrochloric acid, and a further feed for the base-containing product, for example sodium hydroxide solution. In this example the further feed in particular comprises a valve means to control, for example to increase or to reduce, the inflow of the sodium hydroxide solution, i.e. the manipulated variable. This is typically effected depending on the measured actual pH of the mixture in the reaction chamber.
However, one problem herewith is that a controller apparatus having a pH controller set up for controlling the valve means must be operated nonlinearly. The reason for this is that the manipulated variable, such as the inflow of aqueous sodium hydroxide, influences the controlled variable, i.e. the pH to be controlled, nonlinearly on account of dissociation of water, the equilibrium of acid and conjugate base/of base and conjugate acid and logarithmic detection of the H3O+ concentration. In the relevant pH range an orders of magnitude change in the influence of the manipulated variable on the pH takes place. The control process therefore requires complex adjustment of the controller parameters via gain scheduling (variation of controller gain depending on measured pH).
Particularly for large deviations from the target pH (for example by >pH 2) it is additionally necessary for the controller to undertake aggressive alteration of the manipulated variable. This is difficult to implement particularly for a pH controller.
The problem addressed by the present invention is accordingly that of providing a neutralization plant which allows improved control of a neutralization process in simple fashion.